Chumak H. Electromagnetic-spin excitations in ferrites and weak ferromagnetics

The thesis is devoted to the solution of problems of development of disk ferrite resonators magneto-dielectric eigen-oscillations frequencies splitting analytical theory, studying of effects of electromagnetic waves reflection from layered structures based on ferrites and weak ferromagnets, development of microwave range magnon-plasmon-polaritons theory in composite structures with uniaxial ferrites. The thesis consists of five sections. The first section is devoted to a review of the literature on the topic of the dissertation. It discusses the basics of classical electrodynamics of magnetically ordered media and methods of magnetic permeability tensorsobtaining, reviews the classification of magnetically ordered materials such as cubic ferrites, uniaxial hexaferrites, weak ferromagnetic with “easy plane” anisotropy type and theirs magnetic characteristics. A review of the publications on the effect of frequency splitting of azimuthally-inhomogeneous magneto-dielectric modes in ferrite disk resonators is carried out, and the problem of constructing an analytical approximate theory of the effect is set. In this section the main theoretical works devoted to the reflection of electromagnetic waves from layered structures with ferrites are listed. Their main disadvantage, namely the absence of phase dependences of the complex reflection coefficient of electromagnetic waves from such structures, is pointed out and the problem of in-depth study of the electromagnetic waves reflection effects from layered structures with ferrites and weak ferromagnets is formulated. The known literature on surface plasmon-polaritons is analyzed. It is noted that despite the widespread use of surface plasmon-polaritons in the optical range, their studies in the microwave range are insufficient. The problem of developing a more complex theory of magnon-plasmon-polaritons in the millimeter range is formulated. In the second section of the thesis it is shown that the effect of frequency splitting of magneto-dielectric modes can be used in reciprocal and non-reciprocal devices of centimeter, millimeter and submillimeter waveranges. In the sectionan unambiguous correspondence between the polarization of magneto-dielectric modes of cylindrical symmetry resonators and signs "+" and "-" of azimuthal indices, which describe the distributions of electromagnetic fields of these modes was demonstrated. An analytical approximate formula for the calculation the magnitude of the frequency splitting of azimuthally inhomogeneous degenerate modes of a ferrite disk resonator in both above resonant and below resonant regionswas also found. Thus, for various types of ferro-garnets and ferro-spinels in the aboveresonance region, the splitting amounted to 0.56-5.6 GHz and 5.6-14 GHz, respectively. It is noted that, in contrast to ferro-garnets and ferro-spinels, in hexaferrites the effect takes place in both above resonant and below resonant regions and its value varies between 2.8-16.8 GHz and 4-17 GHz, respectively. A satisfactory coincidence between theoretically calculated splitting values and the results of experimental studies of this effect in the millimeter range, presented in the literature, is obtained. It was proposed to consider this effect as an alternative to ferromagnetic resonance in the millimeter range, with such advantages as the possibility of using small magnetic fields and set the initial frequency of the resonator by varying its geometric dimensions.